Tuning fork



July 7, 1925. 1,545,251

y E. W. GENT TUNING FORK Filed July 5, 192.3 2 Sheets-Sheet l fa W/ ffmIMIHUIIIIIIIIIIIIIIIIIlllllllllllllIIlllllllllllllulllllllll July 7,1925. E. w. GENT TUNING Fonx Filed July i925 2 Sheets-Sheet 2 PatentedJuly 17, *192s UNITED STATES 1,545,251 PATENT -oFFlcE.

EDGAR W. GENT, QF IORBISTOWN, NEW JERSEY, ASSIGNOB T WBTEBN ELECTRIG- YY' COMPANY, INCORPORATED, 0F NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

"rome roam Application :Illed July 3,

y full, clear, concise, and exact description.-

'lliis'inventionrelates to tuning forks and particularly to means foraccurately altering the period of vibration of these devices while'inoperation. Y

Oneofthe eaturesof the invention re- .sides in the provision of meansfor altering the frequency of tuning forks and similar` apparatus bychanging the elfective length of the vibratingmasses wliile the fork isin motion.

yAnother. fea-ture involves making this 4change without causing anychange 'in the actual vibratmg length of the tines. That is, the tinesare allowed to vibra-te freely and are not subject to the influence ofany forces extraneous to them.

A further feature is the provision of I means for indicating accuratelyat all times the frequency at which the fork is vibrating.

The change in elfectivelength of the? vibrating masses is accomplishedby controlling the positionvof Weights on the tines bv y manipplating aknrled handle and wheel,

the :latter being mounted on a shaft carrying pinionswhich engagetoothed racks. These racks are caused `to move longitudinally along thetines in slots cut into the underY sides of the tines. In movingthey'carry y with them the weights which are held by means ofprojections on the racks.

-Since the racks fit snugly in the slots in the tines they follow thevibrations of the fork. Tlieracks, tines and weights vibrate as a unit.v

These and other features of the invention f 'win be fully set forth inthe-following de scription and claims, and will be readily understood'by reference to the accompanying drawings, wherein Fig. 1 is a planview of the preferred embodiment; Fig. 2 is a side elevation, the rea-rend being cut away to show the rack and pinion; Fig. 3 is a. sectionalong the line 3 3 in Fig. 1 and shows v the fork showin the operatingcoil; Fig. 4 is an end view of the weights on etines'; F" 5 is anenlargement of the section along e. line 5 5 the methodv of mounting1823. Serial No. 649,19.

.of Fig. 1 showing an arrangement .for convertinf direct current toalternating current; ig. 6 is a section along the line 6-6 of Fig. 1 andshows more clearly the method of controlling the movement of the racks;Fig. 7 is a vlew of the rack itself, showing means for gripping theweights and the teeth for engaging the pinins.

It will 'be readily understood that the tines of the fork describedherein may.. Vbe set in vibration by striking and may be maintained invibration by means of an electromagnet in a well known manner.

The tuning fork and auxiliary parts are mounted on a base 1 which may beo any suitable material for forming a rigid support. This base isarranged with rubber `studs on its under side permitting it to be movedabout without subjecting the fork to undesired shocks. fastened to thebase by means of suitable slotted head bolts 4, and associated nuts 7,

I the tines being allowed to project above and parallel to the base topermit free vibration. Slidably mounted on each tine is a Weightconsisting of two parts clamped together by arscrew 9 having a slottedand knurled head to permit easy adjustment. Associatedwith this screw isa cup-shaped washer l10` which causes the weight to maintain a rin gripon the tine to prevent rattling `of the The shank 2 is irmly- 7 weightand resultingr inaccuracies while the M fork is in vibration. 'The lowerhalf of each weight is gripped between projections 12 and 13 of a. rack14. These racks are embedded in slots cut into the under side of thetines along their central line of vibration. VYThese slots run the fulllength'V of the fork-permitting: the racks to extend upwardfrom theshankof the fork. The 'Y racks are controlled by means of teeth cutalong their upper edges which teeth are engaged by pmions 15.- i.Thelatter are 1 moun on a. common shaft 16 extending Ythrough the shankYand terminating in a knurled wheel 17 mountedl thereon a kn'urled handle18. Theshandle is used for making 'coarse adjustments of the weights andthe wheel for finer adjustments. Suitably mounted on the end of one-ofthe racks is a. pointer 19 which is caused to pa over a scale 20, undercontrol of the knurled. handlel and wheel. This scale may be calibratedtoread in convenient units, preferably the number of vibrations of thefork and the frequency in cycles per second of the current output of thefork.

the coil are brought out through the base to terminals 21 forconveniently connecting to its source of energizing current.. Terminals22 are provided for connectlng to the source of direct current which isto be l converted to 'alternating current. Leads from'these terminalsare suitably mounted in -base 1 and connect respectively to theAvibrating contacts 24 and 25. By making the proper cross connectionswith contacts 26, 27, 28 and 29, a reversing switch is obtained and analternating current is formed in the Well known manner.' Thisocurrentmay be conducted by suitable leads to terminals 23 from which it may bedistributed to serve its particular purpose. v

It Will readily be seen that if while ,the fork isv in vibration itbecomes desirable to change the frequency of the fork, this may easilybe done by turning the handle 18 thereby rotating shaft 16, pinions 15and racks14, causing the Weights 8 to slide forward or backwarddepending upon the direction of rotation of the handle 18. The desiredfrequency may be obtained by a reference to scale 20 and pointer 19. Ifa high degree ,of accuracy is desired wheel 17 ma be manipulated afteran approximate a justment with handle 18.'

.What is claimed is:

1. In a tuning fork, tines, weights suitably mounted onsaid tines forlongitudinal movement with respect to said tines andv means to vary theposition of said, weights with respect to said tines while said fork isin vibration, said means bearing such a relation to said tines that saidtines are free to -vibrate throughout their `entire length. 2. Inatuning fork, tines, weights suitably mounted on said tines forlongitudinal movement with respect to said'tines, means to vary theposition of said Wei hts with respect to saidtines while said ork is invibration, an indicating device, and means to operate said indicatingdevice during said variation to indicate the frequency of vibration ofsaid fork.

3. In a. tuning fork, tines, Weights slidably mounted on said tines,operating mem- 'bers for said Weights, bearing surfaces for saidoperating members within said tines,

and means to vary the position of said f Weights with respect to saidtines by means of said operating members.

- 4. In a tuning fork, tines, Weights slidably mounted on said tines,racks slidably mounted in said tines, said Weights being secured-to saidracks, and a driving mechanism to simultaneously operate sald racks tovary the position of said weights with respect to said tines. y

5. In a tuning fork, tines, weights slidably mounted on said tines,racks slidably mounted in said tines, said weights being secured to saidracks, a driving mechanism to operate said racks tovary the sition ofsaid weights with respect to sai tines, an indicator carried by one ofsaid racks, and means to operate said indicator during movement of saidracksto indicate the frequency of said fork.

In Witness whereof, I hereunto subscribe my'name this 2nd`da of Jul A.D., 1923.

